All things Green Pre

[peterc]

Kato

The 3 left hand caps are all 47uF/63v. The top one in my pic was a different make that I had in my parts box. Could also have been a 100uF/63v cap that I had.

Cant remember exactly, it was a while ago, either value will work great. The 48v is regulated at the PSU, so it is not necessary to puit in a 100v part here.

Peter

 

[AudioJunkie]

I used my dual Green for one of my regular recording gigs. This time was in a different venue. I normally have some very very slight hum on one channel usually down around 60Hz give or take a bit. Usually throwing a low cut when I edit takes care of it.

But this time it was smack dab at 120Hz, plus in real quiet spots, it looks like I'm getting harmonics as well. Not much I can do now, but any ideas if that's something going in the circuit? or some sort of interference?

I never did secure my mains transformer, used some adhesive backed dual sided tape stuff and it's very likely that the transformer had come loose and repositioned itself a bit. Been meaning to screw that down sometime.

Daniel

 

[kato]

[quote author="peterc"]The 3 left hand caps are all 47uF/63v. The top one in my pic was a different make that I had in my parts box. Could also have been a 100uF/63v cap that I had.
[/quote]

Ah, larger capacitance, not greater voltage. Hadn't thought of that.
Thank you Peter, very nice of you to patiently answer so many questions.

I originally stufffed the lower three 47uF's (like an L shape at the bottom left of the board) with 63v's from PtownKits. Then followed the traces and realized that made no sense. Then looked back at your example. Then ordered some new 63v from Mouser. So I've got 4 63v caps in at four corners of a square. It looks like you used larger values in all 4 positions too so it can't hurt. I like putting in larger values wherever I can get away with it. I have to avoid the urge to put in a larger value just because the footprint is bigger in some places - for no other reason than ... they ... fit ... better... :roll: [completely anal impulse.]

By the way, none of this is a question. I'm just rambling. Not really sure why.

I was contemplating what kind of market there would be for an audio electronics book (I work for a publisher.) Thinking out loud, I was trying to explain to my wife what kind of person sits around soldering hundreds of little connections on a board, and then has the patience to troubleshoot the bad joints, source all the parts, etc. (i.e. a small potential readership.)

She said, "And somehow that (referring to a green board) gets used to make music... [pause]
Those are two different personalities."

Yes, I suppose most of the time they are.

Kato

Thank you special people who can relate.
People who otherwise, I would never likely meet.

 

[Phrazemaster]

Hi gang, I had originally posted this in the "newbie green" thread, but Godders suggested I post it here instead. My questions are beginners and possibly obvious or stupid for some of you; sorry. But here goes.

In the pix Peter sent me (thank-you Peter!) I see a set of 3 pins which I connect to the power xformer (sorry I don't have these posted online or I'd put them in here). I am wondering what sort of part these are? They look like straight pins of some kind. I did a search on mouser for "PCB Pins" and just got a morass of confusing results. It also looks like there are three short wires with connectors connecting to those three pins coming from the xformer. What sort of pins/wire connectors are these?

Another question is about the connection from the PSU to the individual PCB's. In the pix from Peter the PSU board has 4 terminal block screws. In another pix from him (and other pix I saw elsewhere) there appears to be a different type of connector, something like a 4-pin molex conn. Which is better, and does anyone have a part# for any of these items? I tried to measure the pins on the PSU pix from Peter in my drawing program, but the measurements wouldn't come out right, so I couldn't tell if the pin spacings were 3.81 or 5mm or what.

Sorry if this is a rambling mass, just trying to get the right parts.

Thanks for any help everyone. I'm sure this is the first of many other q's I'll have, and yes I have been poring over the green meta and using the famous Search function.

 

[fantomas]

Hello i am having some problems with my green pre.

I have made a mistake (short circuit) and blow a couple of resistors. i replaced them and the voltages were very off.
then i realized that the first 47uf caps should be 63 volts (mine were 35v)
i replaced them.
Them i replaced the transistors and all the voltages looks ok except:
ic1 pin2 = 0 volts.


Tanx

 

[fantomas]

hello again (this is the endless debug)
I have found a broken trace and now the voltages are ok.

My question now is that when i engage the phantom power the voltages change a lot and when i turn the phantom off the voltages takes like 5 minutes to get back to the normal readings. Is this normal?

can i put the ics without being afraid to burn something?

thanks

 

[dissonantstring]

fantomas,
if you got your pcbs from peter he would have supplied you with a list of reference voltages without and with ICs. you can check the threads (i believe i saw it listed somewhere, though i may be wrong). if not, PM me and i'll send you the document with the reference voltages. check the voltages without the ICs and if all looks good then pop them in.
regards,
grant

 

[fantomas]

i made my own board. And the voltages are ok according to the refetence chart. Its just that i dont want to burn anything else ( i went twice in a day to the electronics shop) :grin: .

This has been an etude in debugging for me.
i have learned a lot.

thank you

 

[Phrazemaster]

Dang 22pf caps!

Sorry I know this has been mentioned a couple times on the boards but I can't seem to find any WIMA caps at 22pf for the green. I also can't seem to find any poly caps in this range.

Where did you guys find them? I know it was mentioned that ceramic vs poly doesn't matter *that* much but dang it if its a little bit then why not get the better.

So what gives? Whose got a link or part number for some high quality 22pf caps for the green pre?

EDIT: OK OK I found one! But yer not gonna like it, and neither do I, but here's a link....

Farnell Part # 9519971

I'll keep looking, but in the meantime, if you have a source, LEMME NO!

 

[louder]

alo
i used c0g/npo for 22pf.
since you`re in the usa,try mouser or digikey.
best regards
pedro

 

[Phrazemaster]

Hi pedro, thanks for the reply. I have mouser'ed it and digikey'ed it but didn't find any poly caps in this range. I found mica and ceramics though.

Maybe it really doesn't matter?

 

[kato]

[quote author="Phrazemaster"]
I'd put them in here). I am wondering what sort of part these are? They look like straight pins of some kind. I did a search on mouser for "PCB Pins" and just got a morass of confusing results. It also looks like there [/quote]

Hey, we're building our greens at the same time.
I stuffed my boards a while ago but I'm only now getting around to racking them.

The most common pin spacing for those kind of connectors is .1". (You'll also sometimes see .156" on projects with thicker traces (like LA2A PCB.)

Molex is a brand. They make several products - but people often call those "molex connectors" as a generic.

I just placed my mouser order some of these connectors yesterday:

2-pin housing: 538-22-01-2027
2-pin header: 538-22-23-2021

3-pin housing: 538-22-01-2037
3-pin header: 538-22-23-2031

4-pin housing: 538-22-01-2047
4-pin header: 538-22-23-2041

[EDIT] Edited the mouser catalog numbers above swapping regular vertical headers for "friction lock" headers and plain housings for ones with locking ramps. I've ordered them before and like them better (more expensive though.)

from mouser catalog pg. 1179 and thereabouts.

oh yeah, and pins.

 

[Phrazemaster]

you rock kato! thank-you!!!!

 

[louder]

alo
c0g/npo,are ceramic caps.
i don`t think you`ll find 22pf in poly.
get the c0g and get on with it.
best regards
pedro

 

[Phrazemaster]

Well half the fun is finding the best I can find. Otherwise I suppose I could just use my Mackie for pres.

 

[kato]

[quote author="Phrazemaster"]Sorry I know this has been mentioned a couple times on the boards but I can't seem to find any WIMA caps at 22pf for the green. I also can't seem to find any poly caps in this range.
[/quote]

You won't. Ceramics are your only option in this range / value.

[quote author="Phrazemaster"]
Where did you guys find them? I know it was mentioned that ceramic vs poly doesn't matter *that* much but dang it if its a little bit then why not get the better.[/quote]

You could use these.

Not all ceramics are created equal.
(ie, not all are bad.)
Use ones with this dialetic material: C0G or NP0. Avoid X7R for audio.

Read page 8 of this PDF from John Hardy for a discussion of which ceramics are good / which are not.

I used Epcos C0G 22pF caps for the Green.
(digikey has a much better cap selection than mouser. although I use mouser for almost everything else.) i have no reason to believe the epcos are any better than the xicon. the price is the same (6¢ vs. 8¢) The only reason I use epcos is because they're blue and I think they look cool. :roll:

 

[Phrazemaster]

Once again I'm indebted to you kato, thx!

By the way I *did* find a source for polystyrene's in 22pf. I don't know how these stack up, but you might check it out.

Parts Connection

You have to look at the bottom of the web page; there are some funny little tabs there and click the one labelled Polystyrene.

Thx again everyone!

 

[peterc]

Polystyrene are good for the 22pF, as are npo/cog ceramics. As was mentioned above, dont go to the X7/Y5 types, they are the types that gave ceramics a bad name!

Fantomas:

My question now is that when i engage the phantom power the voltages change a lot and when i turn the phantom off the voltages takes like 5 minutes to get back to the normal readings. Is this normal?

Which voltages change? The phantom could go as low as 30v or so depending on the mike, & the recovery time is long because of the 47uF smoothing cap on the phantom line.

 

[Phrazemaster]

Thanks Peter!

I also found another source for the polystyrene 22pf's, although they are pricey.

JustRadios.com




[EDIT: found same caps from same dealer on evilbay, $10 for 8, bought two lots...oh the madness!!!]

 

[Phrazemaster]

Question gang: would 1/2W resistors fit on the Green PCBs, and is there any advantage whatsoever to doing so?

I like to overbuild everything, but if the 1/2W ones just won't fit, I won't order those.

And by the way, does the brand matter at all? So far I have just spec'ed some Xicon's at Mouser. Panasonic better? Some other brand? I didn't find too much on the board here about brands.

Thanks,

Mike :grin: